```json
{
	"no": ["no"],  
	"yes": ["yes"]
}
```

Based on the given description, the feature `ritm_ecg_p_04`, which represents the ECG rhythm at the time of admission to the hospital, is a categorical variable with two possible categories: "no" and "yes". For this task, we are interested in determining whether the patient has chronic heart failure based on the myocardial infarction complications data.

Since there are only two possible values for `ritm_ecg_p_04`, namely "no" and "yes", we can create a dictionary showing the possible values of `ritm_ecg_p_04` for each target class.

In the case of the target class "no" (the patient does not show chronic heart failure), the possible values of `ritm_ecg_p_04` are ["no"].

In the case of the target class "yes" (the patient shows chronic heart failure), the possible values of `ritm_ecg_p_04` are ["yes"].

Keep in mind that, for this particular feature, we are assuming that there are no additional categories beyond "no" and "yes".